The present invention relates to a packet-switching system having a buffer memory for storing received packets, and more particularly, to a packet-switching system which can perform a high-speed, one-dimensional control of the buffer memory.
Recently, the data communication method, generally called "packet switching", has been put to practical use in various places. In this method, the data to be transmitted is divided into data blocks of a predetermined length. The destination address and control data are attached to each of these data blocks, thus forming a packet. The data is transmitted or exchanged, packet by packet. The data transmitted from a transmitting station is temporarily stored in the buffer memory provided in a packet-switching system. The data is processed in accordance with the destination address and the control data, and is then transmitted to a receiving station, also packet by packet.
Hitherto, the buffer memory used in the packetswitching system has been controlled in the following way. The storage area of the memory is divided into a plurality of regions of the same size. Of these regions, those storing no data are detected. A list of the start addresses of the vacant regions is prepared. This list is referred to, thereby identifying the vacant regions of the buffer memory, and the received data is stored into those vacant regions. As soon as data is read out from any region and subsequently transferred to the receiving station, this region is regarded as vacant, and its start address is added to the list.
This method of controlling the buffer memory, which is accomplished with reference to the list of the start addresses of vacant regios, can indeed help to enhance the use efficiency of the buffer memory, provided the size of the regions is sufficiently small. However, it takes rather a long time to identify the vacant regions by referring to the list. Today, the data-transfer speed has increased very much, and the buffer memory of the packet-switching system should now be controlled at a higher speed.